DESCRIPTION (adapted from the Abstract): This is an application for five years of support to identify and characterize glial chemokine receptors. The Principal Investigator and associates will determine which of the known chemokine receptors are expressed on murine astrocytes and microglial cells, and whether these receptors are functionally active by assaying for their ability to mediate second signals or chemotactic responses. Two specific aims are proposed. In the first, the researchers will identify the chemokine receptors that are expressed on glial cells by first looking at the expression of known murine chemokine receptors, then identify novel chemokine receptors using molecular techniques, and, when those are obtained, express those chemokine receptor proteins in high quantities such that they can then be used to accomplish the goals of Aim #2. In this aim, the researchers will examine the activity of chemokines on glia and look at chemokine receptor specificity and modulation. The Investigator proposes that in some instances a desensitization of chemokine responses occurs; the researchers will examine this, as well. Further, the Investigator offers preliminary data that suggest that in some instances a chemostasis (rather than a chemotactic) response occurs; the researchers will study this, also. In support of the application, the Investigator includes preliminary data that demonstrate the researchers' ability to isolate and purify chemokine receptors. He shows, also, that he has considerable experience in analyzing chemokine receptor binding. He has developed assays to look at astrocytic chemotaxis and presents convincing data that demonstrate that mouse astrocytes migrate in response to chemokines like MIP-1 alpha and eotaxin and that those chemokine receptors are expressed in glia. Specifically, he has shown the presence of CCR1 and CXCR4 in astrocytes and, possibly, of CCR5, as well. Although astrocytes have CXCR4, they do not appear to respond with chemotaxis after stimulation with the CXCR4 ligand, the chemokine SDF-1.